#include <iostream>
#include <cstring>
#include <string>
// #pragma warning(disable : 4996)
using namespace std;
int main(void) {
// freopen("input.txt", "r", stdin);
int checked[10] = { 0, };
int count = 1;
char arr[1000001];
cin >> arr;
for (int i = 0;i < strlen(arr);i++)
{
if (checked[arr[i] - 48] == 0) // 체크 안 됬을 때
{
checked[arr[i] - 48] = 1; // 체크
continue;
}
else // 체크 됬다면
{
if (arr[i] - 48 == 6) // 6이 체크 됬을 때
{
if (checked[(arr[i] - 48) + 3] == 0) // 9 체크 안됬으면 9 체크
{
checked[(arr[i] - 48) + 3] = 1;
continue;
}
else // 6, 9 둘다 체크
{
count++;
checked[6] = 1;
checked[9] = 0;
continue;
}
}
else if (arr[i] - 48 == 9) // 9가 체크 됬을 때
{
if (checked[(arr[i] - 48) - 3] == 0) // 6 체크 안됬다면 6체크
{
checked[(arr[i] - 48) - 3] = 1;
continue;
}
else // 9, 6 둘다 체크
{
count++;
checked[9] = 1;
checked[6] = 0;
continue;
}
}
else
{
count++;
continue;
}
}
}
cout << count << endl;
return 0;
}
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